第工作中禁止使用Executors快捷創(chuàng)建線程池原理詳解目錄問(wèn)題？1.1newFixedThreadPool的潛在問(wèn)題1.2newSingleThreadExecutor的潛在問(wèn)題？1.3newCachedThreadPool的潛在問(wèn)題1.4newScheduledThreadPool潛在問(wèn)題1.5總結(jié)

問(wèn)題？

在很多公司（如阿里、華為等）的編程規(guī)范中，非常明確地禁止使用Executors快捷創(chuàng)建線程池，為什么呢？這里從源碼講起，介紹使用Executors工廠方法快捷創(chuàng)建線程池將會(huì)面臨的潛在問(wèn)題。

1.1newFixedThreadPool的潛在問(wèn)題

基本使用

//線程池

ExecutorServicesingleThreadExecutor=Executors.newFixedThreadPool(2);

//批量添加線程

for(inti=0;ii++){

singleThreadExecutor.execute(newTargetTask());

//singleThreadExecutor.submit(newTargetTask());

Thread.sleep(1000);

//線程池銷毀

singleThreadExecutor.shutdown();;

查看源碼

publicstaticExecutorServicenewFixedThreadPool(intnThreads){

returnnewThreadPoolExecutor(nThreads,nThreads,

0L,TimeUnit.MILLISECONDS,

newLinkedBlockingQueueRunnable

*Createsa{@codeLinkedBlockingQueue}withacapacityof

*{@linkInteger#MAX_VALUE}.

publicLinkedBlockingQueue(){

this(Integer.MAX_VALUE);

我們可以看出：

corePoolSize(核心線程數(shù))=maximumPoolSize（最大線程數(shù)）。LinkedBlockingQueue是一個(gè)無(wú)界隊(duì)列，如果提交的任務(wù)過(guò)快會(huì)造成任務(wù)大量的的堆積，消耗完服務(wù)器資源。如果隊(duì)列很大，很有可能導(dǎo)致JVM出現(xiàn)OOM（OutOfMemory）異常，即內(nèi)存資源耗盡。

1.2newSingleThreadExecutor的潛在問(wèn)題？

基本使用

//線程池

ExecutorServicesingleThreadExecutor=Executors.newSingleThreadExecutor();

//批量添加線程

for(inti=0;ii++){

singleThreadExecutor.execute(newTargetTask());

//singleThreadExecutor.submit(newTargetTask());

Thread.sleep(1000);

//線程池銷毀

singleThreadExecutor.shutdown();;

查看源碼

publicstaticExecutorServicenewSingleThreadExecutor(){

returnnewFinalizableDelegatedExecutorService

(newThreadPoolExecutor(1,1,

0L,TimeUnit.MILLISECONDS,

newLinkedBlockingQueueRunnable()));

*Createsa{@codeLinkedBlockingQueue}withacapacityof

*{@linkInteger#MAX_VALUE}.

publicLinkedBlockingQueue(){

this(Integer.MAX_VALUE);

嘗試修改核心線程數(shù)

packageExecutorDemo.newSingleThreadExecutor;

importjava.util.concurrent.ExecutorService;

importjava.util.concurrent.Executors;

importjava.util.concurrent.ThreadPoolExecutor;

*@description:

*@author:shu

*@createDate:2025/11/110:45

*@version:1.0

publicclassUpdateSingleThreadExecutor{

publicstaticvoidmain(String[]args){

//創(chuàng)建一個(gè)固定大小的線程池

ExecutorServicefixedExecutorService=

Executors.newFixedThreadPool(1);

ThreadPoolExecutorthreadPoolExecutor=

(ThreadPoolExecutor)fixedExecutorService;

System.out.println(threadPoolExecutor.getMaximumPoolSize());

//設(shè)置核心線程數(shù)

threadPoolExecutor.setCorePoolSize(8);

//創(chuàng)建一個(gè)單線程化的線程池

ExecutorServicesingleExecutorService=

Executors.newSingleThreadExecutor();

//轉(zhuǎn)換成普通線程池，會(huì)拋出運(yùn)行時(shí)異常java.lang.ClassCastException

((ThreadPoolExecutor)singleExecutorService).setCorePoolSize(8);

我們可以看出：

單例存在，我們無(wú)法去修改核心線程數(shù)，否則會(huì)造成異常處理。corePoolSize(核心線程數(shù))=maximumPoolSize（最大線程數(shù)）=1。LinkedBlockingQueue是一個(gè)無(wú)界隊(duì)列，如果提交的任務(wù)過(guò)快會(huì)造成任務(wù)大量的的堆積，消耗完服務(wù)器資源。如果隊(duì)列很大，很有可能導(dǎo)致JVM出現(xiàn)OOM（OutOfMemory）異常，即內(nèi)存資源耗盡。

1.3newCachedThreadPool的潛在問(wèn)題

基本使用

//線程池

ExecutorServicesingleThreadExecutor=Executors.newCachedThreadPool();

//批量添加線程

for(inti=0;ii++){

singleThreadExecutor.execute(newTargetTask());

//singleThreadExecutor.submit(newTargetTask());

Thread.sleep(1000);

//線程池銷毀

singleThreadExecutor.shutdown();;

源碼分析

publicstaticExecutorServicenewCachedThreadPool(){

returnnewThreadPoolExecutor(0,Integer.MAX_VALUE,

60L,TimeUnit.SECONDS,

newSynchronousQueueRunnable

*Createsa{@codeSynchronousQueue}withnonfairaccesspolicy.

publicSynchronousQueue(){

this(false);

ThreadPoolExecutor標(biāo)準(zhǔn)構(gòu)造器創(chuàng)建一個(gè)核心線程數(shù)為0、最大線程數(shù)不設(shè)限制的線程池理論上可緩存線程池可以擁有無(wú)數(shù)個(gè)工作線程，即線程數(shù)量幾乎無(wú)限制?？删彺婢€程池的workQueue為SynchronousQueue同步隊(duì)列，這個(gè)隊(duì)列類似于一個(gè)接力棒，入隊(duì)出隊(duì)必須同時(shí)傳遞，正因?yàn)榭删彺婢€程池可以無(wú)限制地創(chuàng)建線程，不會(huì)有任務(wù)等待，所以才使用SynchronousQueue。但是，maximumPoolSize的值為Integer.MAX_VALUE（非常大），可以認(rèn)為可以無(wú)限創(chuàng)建線程，如果任務(wù)提交較多，就會(huì)造成大量的線程被啟動(dòng)，很有可能造成OOM異常，甚至導(dǎo)致CPU線程資源耗盡。

1.4newScheduledThreadPool潛在問(wèn)題

基本使用

//線程池

ScheduledExecutorServiceservice=Executors.newScheduledThreadPool(2);

//批量添加線程

for(inti=0;ii++){

ScheduledFuturefuture=service.scheduleWithFixedDelay(newTargetTask(),0,500,TimeUnit.MILLISECONDS);

Thread.sleep(1000);

//線程池銷毀

service.shutdown();;

源碼分析

publicScheduledThreadPoolExecutor(intcorePoolSize){

super(corePoolSize,Integer.MAX_VALUE,0,NANOSECONDS,

newDelayedWorkQueue());

staticclassDelayedWorkQueueextendsAbstractQueueRunnable

implementsBlockingQueueRunnable{

privatestaticfinalintINITIAL_CAPACITY=16;

privateRunnableScheduledFuture[]queue=

newRunnableScheduledFuture[INITIAL_CAPACITY];

privatefinalReentrantLocklock=newReentrantLock();

privateintsize=0;

privateThreadleader=null;

privatefinalConditionavailable=lock.newCondition();

maximumPoolSize為Integer.MAX_VALUE，表示線程數(shù)不設(shè)上限，其workQueue為一